Chromatin structure analysis of the rat Na, K-ATPase beta2 gene 5'-flanking region

The Na, K-ATPase is formed by two major subunits (alpha and beta) encoded by a gene family of at least four alpha and three beta isoforms. These genes show distinctive expression patterns involving complex tissue-specific and developmental regulation, although the control mechanisms are not well understood. Here we study the role of chromatin structure in the tissue-specific expression of rat Na, K-ATPase beta2 isoform, which is mainly found in the central nervous system. We have examined the presence and characteristics of nuclease hypersensitive sites and the cytosine methylation patterns in the 5'-flanking region of the beta2 isoform gene from various nuclear preparations. Our results show that in this 5'-flanking region there is only one nuclease hypersensitive site. It is located upstream of the transcription initiation site and shows tissue-specific characteristics. Digestion with deoxyribonuclease I (DNase I), S1 nuclease and micrococcal nuclease yield patterns consistent with a triple-helix structure present only in the active state of the promoter. We also demonstrate that the 5'-flanking region of the beta2 gene co-localizes with a CpG island free of methylation in every tissue tested. The results presented here support a role for specific chromatin remodeling events in the regulation of the Na, K-ATPase beta2 gene expression. They also provide the basis for future studies of the transcription factors involved in the regulation of this gene.